The third-party doctrine states that an individual cannot claim a legitimate expectation of privacy for information that the he voluntarily conveyed to a third party and therefore the information is not subject to Fourth Amendment protection. In a world of technology that relies on third-party service providers, this doctrine has a drastic impact on the constitutional protection against unreasonable search and seizure. The government has used this principle in order to access personal information stored by cellphone companies and internet service providers without a search warrant. Many consider this a dangerous and escalating invasion of privacy by our government. See our full article here for a brief history and the current usage of the third-party doctrine.